bsd.README revision 1.69
1#	$NetBSD: bsd.README,v 1.69 2000/10/04 19:27:45 sommerfeld Exp $
2#	@(#)bsd.README	8.2 (Berkeley) 4/2/94
3
4This is the README file for the new make "include" files for the BSD
5source tree.  The files are installed in /usr/share/mk, and are, by
6convention, named with the suffix ".mk".
7
8Note, this file is not intended to replace reading through the .mk
9files for anything tricky.
10
11=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
12
13RANDOM THINGS WORTH KNOWING:
14
15The files are simply C-style #include files, and pretty much behave like
16you'd expect.  The syntax is slightly different in that a single '.' is
17used instead of the hash mark, i.e. ".include <bsd.prog.mk>".
18
19One difference that will save you lots of debugging time is that inclusion
20of the file is normally done at the *end* of the Makefile.  The reason for
21this is because .mk files often modify variables and behavior based on the
22values of variables set in the Makefile.  To make this work, remember that
23the FIRST target found is the target that is used, i.e. if the Makefile has:
24
25	a:
26		echo a
27	a:
28		echo a number two
29
30the command "make a" will echo "a".  To make things confusing, the SECOND
31variable assignment is the overriding one, i.e. if the Makefile has:
32
33	a=	foo
34	a=	bar
35
36	b:
37		echo ${a}
38
39the command "make b" will echo "bar".  This is for compatibility with the
40way the V7 make behaved.
41
42It's fairly difficult to make the BSD .mk files work when you're building
43multiple programs in a single directory.  It's a lot easier split up the
44programs than to deal with the problem.  Most of the agony comes from making
45the "obj" directory stuff work right, not because we switched to a new version
46of make.  So, don't get mad at us, figure out a better way to handle multiple
47architectures so we can quit using the symbolic link stuff.  (Imake doesn't
48count.)
49
50The file .depend in the source directory is expected to contain dependencies
51for the source files.  This file is read automatically by make after reading
52the Makefile.
53
54The variable DESTDIR works as before.  It's not set anywhere but will change
55the tree where the file gets installed.
56
57The profiled libraries are no longer built in a different directory than
58the regular libraries.  A new suffix, ".po", is used to denote a profiled
59object, and ".so" denotes a shared (position-independent) object.
60
61The following variables that control how things are made/installed that
62are not set by default. These should not be set by Makefiles; they're for
63the user to define in MAKECONF (see bsd.own.mk, below) or on the make(1)
64command line:
65
66BUILD 		If defined, 'make install' checks that the targets in the
67		source directories are up-to-date and remakes them if they
68                are out of date, instead of blindly trying to install
69                out of date or non-existant targets.
70
71UPDATE 		If defined, 'make install' only installs targets that are
72		more recently modified in the source directories that their
73		installed counterparts.
74
75UNPRIVILEGED	If defined, don't set the owner/group/mode when installing
76		files or directories.  This allows a non-root "make install".
77
78MKCATPAGES	If "no", don't build or install the catman pages.
79
80MKDOC		If "no", don't build or install the documentation.
81
82MKINFO		If "no", don't build or install Info documentation from
83		Texinfo source files.
84
85MKLINT		If "no", don't build or install the lint libraries.
86
87MKMAN		If "no", don't build or install the man or catman pages.
88		Also acts as "MKCATPAGES=no"
89
90MKNLS		If "no", don't build or install the NLS files.
91
92MKOBJ		If "no", don't enable the rule which creates objdirs.
93		"yes" by default.
94
95MKOBJDIRS	If "no", don't create objdirs during a "make build".
96		"no" by default.
97
98MKPIC		If "no", don't build or install shared libraries.
99
100MKPICINSTALL	If "no", don't install the *_pic.a libraries.
101
102MKPROFILE	If "no", don't build or install the profiling libraries.
103
104MKSHARE		If "no", act as "MKCATPAGES=no MKDOC=no MKINFO=no MKMAN=no
105		MKNLS=no".  I.e, don't build catman pages, documentation,
106		Info documentation, man pages, NLS files, ...
107
108=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
109
110The include file <sys.mk> has the default rules for all makes, in the BSD
111environment or otherwise.  You probably don't want to touch this file.
112
113=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
114
115The include file <bsd.man.mk> handles installing manual pages and their
116links.
117
118It has a two targets:
119
120	maninstall:
121		Install the manual page sources and their links.
122	catinstall:
123		Install the preformatted manual pages and their links.
124
125It sets/uses the following variables:
126
127MANDIR		Base path for manual installation.
128
129MANGRP		Manual group.
130
131MANOWN		Manual owner.
132
133MANMODE		Manual mode.
134
135MANSUBDIR	Subdirectory under the manual page section, i.e. "/vax"
136		or "/tahoe" for machine specific manual pages.
137
138MAN		The manual pages to be installed (use a .1 - .9 suffix).
139
140MLINKS		List of manual page links (using a .1 - .9 suffix).  The
141		linked-to file must come first, the linked file second,
142		and there may be multiple pairs.  The files are soft-linked.
143
144The include file <bsd.man.mk> includes a file named "../Makefile.inc" if
145it exists.
146
147=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
148
149The include file <bsd.own.mk> contains source tree configuration parameters,
150such as the owners, groups, etc. for both manual pages and binaries, and
151a few global "feature configuration" parameters.
152
153It has no targets.
154
155To get system-specific configuration parameters, bsd.own.mk will try to
156include the file specified by the "MAKECONF" variable.  If MAKECONF is not
157set, or no such file exists, the system make configuration file, /etc/mk.conf
158is included.  These files may define any of the variables described below.
159
160bsd.own.mk sets the following variables, if they are not already defined
161(defaults are in brackets):
162
163BSDSRCDIR	The real path to the system sources, so that 'make obj'
164		will work correctly. [/usr/src]
165
166BSDOBJDIR	The real path to the system 'obj' tree, so that 'make obj'
167		will work correctly. [/usr/obj]
168
169BINGRP		Binary group. [wheel]
170
171BINOWN		Binary owner. [root]
172
173BINMODE		Binary mode. [555]
174
175NONBINMODE	Mode for non-executable files. [444]
176
177MANDIR		Base path for manual installation. [/usr/share/man/cat]
178
179MANGRP		Manual group. [wheel]
180
181MANOWN		Manual owner. [root]
182
183MANMODE		Manual mode. [${NONBINMODE}]
184
185MANINSTALL	Manual installation type: maninstall, catinstall, or both
186
187LIBDIR		Base path for library installation. [/usr/lib]
188
189LINTLIBDIR	Base path for lint(1) library installation. [/usr/libdata/lint]
190
191LIBGRP		Library group. [${BINGRP}]
192
193LIBOWN		Library owner. [${BINOWN}]
194
195LIBMODE		Library mode. [${NONBINMODE}]
196
197DOCDIR		Base path for system documentation (e.g. PSD, USD, etc.)
198	        installation. [/usr/share/doc]
199
200HTMLDOCDIR	Base path for html system documentation installation.
201		[/usr/share/doc/html]
202
203DOCGRP		Documentation group. [wheel]
204
205DOCOWN		Documentation owner. [root]
206
207DOCMODE		Documentation mode. [${NONBINMODE}]
208
209NLSDIR		Base path for National Language Support files installation.
210		[/usr/share/nls]
211
212NLSGRP		National Language Support files group. [wheel]
213
214NLSOWN		National Language Support files owner. [root]
215
216NLSMODE		National Language Support files mode. [${NONBINMODE}]
217
218STRIPFLAG	The flag passed to the install program to cause the binary
219		to be stripped.  This is to be used when building your
220		own install script so that the entire system can be made
221		stripped/not-stripped using a single knob. [-s]
222
223COPY		The flag passed to the install program to cause the binary
224		to be copied rather than moved.  This is to be used when
225		building our own install script so that the entire system
226		can either be installed with copies, or with moves using
227		a single knob. [-c]
228
229Additionally, the following variables may be set by bsd.own.mk or in a
230make configuration file to modify the behaviour of the system build
231process (default values are in brackets along with comments, if set by
232bsd.own.mk):
233
234MKCRYPTO	If set to "no", no cryptography support will be built
235		into the system.  Defaults to "yes".
236
237NOCRYPTO	If set, it is equivalent to setting MKCRYPTO to "no".
238
239MKCRYPTO_IDEA	If set to "yes", IDEA support will be built into
240		libcrypto_idea.a.  Defaults to "no".
241
242MKCRYPTO_RC5	If set to "yes", RC5 support will be built into
243		libcrypto_rc5.a.  Defaults to "no".
244
245MKKERBEROS	If set to "no", disables building Kerberos (v4 or v5)
246		support into various system utilities that support it.
247		Defaults to "yes".  NOTE: This does not affect the
248		building of the Kerberos libraries or infrastructure
249		programs themselves.  To completely disable Kerberos,
250		set MKCRYPTO to "no".
251
252NOKERBEROS	If set, it is equivalent to setting MKKERBEROS to "no".
253
254SKEY		Compile in support for S/key authentication. [yes, set
255		unconditionally]
256
257MANZ		Compress manual pages at installation time.
258
259SYS_INCLUDE	Copy or symlink kernel include files into /usr/include.
260		Possible values are "symlinks" or "copies" (which is
261		the same as the variable being unset).
262
263NOPROFILE	Do not build profiled versions of system libraries
264
265NOPIC		Do not build PIC versions of system libraries, and
266		do not build shared libraries.  [set if ${MACHINE_ARCH}
267		is "sh3" and ${OBJECT_FMT} is "COFF", unset otherwise.]
268
269NOLINT		Do not build lint libraries.
270
271OBJECT_FMT	Object file format. [set to "ELF" on architectures that
272		use ELF -- currently if ${MACHINE_ARCH} is "alpha",
273		"mipsel", "mipseb", "powerpc", "sparc", "sparc64",
274		and "i386", or set to "a.out" on other architectures].
275
276
277bsd.own.mk is generally useful when building your own Makefiles so that
278they use the same default owners etc. as the rest of the tree.
279
280=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
281
282The include file <bsd.prog.mk> handles building programs from one or
283more source files, along with their manual pages.  It has a limited number
284of suffixes, consistent with the current needs of the BSD tree.
285
286It has eight targets:
287
288	all:
289		build the program and its manual page
290	clean:
291		remove the program, any object files and the files a.out,
292		Errs, errs, mklog, and ${PROG}.core.
293	cleandir:
294		remove all of the files removed by the target clean, as
295		well as .depend, tags, and any manual pages.
296		`distclean' is a synonym for `cleandir'.
297	depend:
298		make the dependencies for the source files, and store
299		them in the file .depend.
300	includes:
301		install any header files.
302	install:
303		install the program and its manual pages; if the Makefile
304		does not itself define the target install, the targets
305		beforeinstall and afterinstall may also be used to cause
306		actions immediately before and after the install target
307		is executed.
308	lint:
309		run lint on the source files
310	tags:
311		create a tags file for the source files.
312
313It sets/uses the following variables:
314
315BINGRP		Binary group.
316
317BINOWN		Binary owner.
318
319BINMODE		Binary mode.
320
321CLEANFILES	Additional files to remove for the clean and cleandir targets.
322
323COPTS		Additional flags to the compiler when creating C objects.
324
325CPPFLAGS	Additional flags to the C pre-processor
326
327LDADD		Additional loader objects.  Usually used for libraries.
328		For example, to load with the compatibility and utility
329		libraries, use:
330
331			LDADD+=-lutil -lcompat
332
333LDFLAGS		Additional loader flags.
334
335LINKS		The list of binary links; should be full pathnames, the
336		linked-to file coming first, followed by the linked
337		file.  The files are hard-linked.  For example, to link
338		/bin/test and /bin/[, use:
339
340			LINKS=	${DESTDIR}/bin/test ${DESTDIR}/bin/[
341
342SYMLINKS	The list of symbolic links; should be full pathnames.
343                Syntax is identical to LINKS. Note that DESTDIR is not
344		automatically included in the link.
345
346MAN		Manual pages (should end in .1 - .9).  If no MAN variable is
347		defined, "MAN=${PROG}.1" is assumed.
348
349PROG		The name of the program to build.  If not supplied, nothing
350		is built.
351
352PROGNAME	The name that the above program will be installed as, if
353		different from ${PROG}.
354
355SRCS		List of source files to build the program.  If SRCS is not
356		defined, it's assumed to be ${PROG}.c.
357
358DPADD		Additional dependencies for the program.  Usually used for
359		libraries.  For example, to depend on the compatibility and
360		utility libraries use:
361
362			DPADD+=${LIBCOMPAT} ${LIBUTIL}
363
364		The following libraries are predefined for DPADD:
365
366		LIBCRT0?=	${DESTDIR}/usr/lib/crt0.o
367		LIBC?=		${DESTDIR}/usr/lib/libc.a
368		LIBC_PIC?=	${DESTDIR}/usr/lib/libc_pic.a
369		LIBCOMPAT?=	${DESTDIR}/usr/lib/libcompat.a
370		LIBCRYPT?=	${DESTDIR}/usr/lib/libcrypt.a
371		LIBCURSES?=	${DESTDIR}/usr/lib/libcurses.a
372		LIBDBM?=	${DESTDIR}/usr/lib/libdbm.a
373		LIBDES?=	${DESTDIR}/usr/lib/libdes.a
374		LIBEDIT?=	${DESTDIR}/usr/lib/libedit.a
375		LIBGCC?=	${DESTDIR}/usr/lib/libgcc.a
376		LIBGNUMALLOC?=	${DESTDIR}/usr/lib/libgnumalloc.a
377		LIBIPSEC?=	${DESTDIR}/usr/lib/libipsec.a
378		LIBKDB?=	${DESTDIR}/usr/lib/libkdb.a
379		LIBKRB?=	${DESTDIR}/usr/lib/libkrb.a
380		LIBKVM?=	${DESTDIR}/usr/lib/libkvm.a
381		LIBL?=		${DESTDIR}/usr/lib/libl.a
382		LIBM?=		${DESTDIR}/usr/lib/libm.a
383		LIBMENU?=	${DESTDIR}/usr/lib/libmenu.a
384		LIBMP?=		${DESTDIR}/usr/lib/libmp.a
385		LIBNTP?=	${DESTDIR}/usr/lib/libntp.a
386		LIBPC?=		${DESTDIR}/usr/lib/libpc.a
387		LIBPCAP?=	${DESTDIR}/usr/lib/libpcap.a
388		LIBPLOT?=	${DESTDIR}/usr/lib/libplot.a
389		LIBPOSIX?=	${DESTDIR}/usr/lib/libposix.a
390		LIBRESOLV?=	${DESTDIR}/usr/lib/libresolv.a
391		LIBRPCSVC?=	${DESTDIR}/usr/lib/librpcsvc.a
392		LIBSKEY?=	${DESTDIR}/usr/lib/libskey.a
393		LIBTERMCAP?=	${DESTDIR}/usr/lib/libtermcap.a
394		LIBTELNET?=	${DESTDIR}/usr/lib/libtelnet.a
395		LIBUTIL?=	${DESTDIR}/usr/lib/libutil.a
396		LIBWRAP?=	${DESTDIR}/usr/lib/libwrap.a
397		LIBY?=		${DESTDIR}/usr/lib/liby.a
398		LIBZ?=		${DESTDIR}/usr/lib/libz.a
399
400
401SHAREDSTRINGS	If defined, a new .c.o rule is used that results in shared
402		strings, using xstr(1). Note that this will not work with
403		parallel makes.
404
405STRIPFLAG	The flag passed to the install program to cause the binary
406		to be stripped.
407
408SUBDIR		A list of subdirectories that should be built as well.
409		Each of the targets will execute the same target in the
410		subdirectories.
411
412SCRIPTS		A list of interpreter scripts [file.{sh,csh,pl,awk,...}].
413		These are installed exactly like programs.
414
415SCRIPTSNAME	The name that the above program will be installed as, if
416		different from ${SCRIPTS}. These can be further specialized
417		by setting SCRIPTSNAME_<script>.
418
419FILES		A list of files to install. The installation is controlled
420		by the FILESNAME, FILESOWN, FILESGRP, FILESMODE, FILESDIR
421		variables that can be further specialized by FILES<VAR>_<file>
422
423The include file <bsd.prog.mk> includes the file named "../Makefile.inc"
424if it exists, as well as the include file <bsd.man.mk>.
425
426Some simple examples:
427
428To build foo from foo.c with a manual page foo.1, use:
429
430	PROG=	foo
431
432	.include <bsd.prog.mk>
433
434To build foo from foo.c with a manual page foo.2, add the line:
435
436	MAN=	foo.2
437
438If foo does not have a manual page at all, add the line:
439
440	NOMAN=	noman
441
442If foo has multiple source files, add the line:
443
444	SRCS=	a.c b.c c.c d.c
445
446=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
447
448The include file <bsd.subdir.mk> contains the default targets for building
449subdirectories.  It has the same eight targets as <bsd.prog.mk>: all, 
450clean, cleandir, depend, includes, install, lint, and tags.  For all of
451the directories listed in the variable SUBDIRS, the specified directory 
452will be visited and the target made.  There is also a default target which
453allows the command "make subdir" where subdir is any directory listed in
454the variable SUBDIRS.
455
456=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
457
458The include file <bsd.links.mk> handles the LINKS and SYMLINKS variables
459and is included from from bsd.lib.mk and bsd.prog.mk.
460
461=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
462
463The include file <bsd.files.mk> handles the FILES variables and is included
464from bsd.lib.mk and bsd.prog.mk.
465
466=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
467
468The include file <bsd.inc.mk> defines the includes target and uses two
469variables:
470
471INCS	The list of include files
472
473INCSDIR	The location to install the include files.
474
475=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
476
477The include file <bsd.kinc.mk> defines the many targets (includes,
478subdirectories, etc.), and is used by kernel makefiles to handle
479include file installation.  It is intended to be included alone, by
480kernel Makefiles.  Please see bsd.kinc.mk for more details, and keep
481the documentation in that file up to date.
482
483=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
484
485The include file <bsd.info.mk> is used to generate and install GNU Info
486documentation from respective Texinfo source files.  It defines three
487implicit targets (.txi.info, .texi.info, and .texinfo.info), and uses the
488following variables:
489
490TEXINFO		List of Texinfo source files.  Info documentation will
491		consist of single files with the extension replaced by
492		.info.
493
494INFOFLAGS	Flags to pass to makeinfo.  []
495
496INSTALL_INFO	Name of install-info program.  [install-info]
497
498MAKEINFO	Name of makeinfo program.  [makeinfo]
499
500=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
501
502The include file <bsd.sys.mk> is used by <bsd.prog.mk> and
503<bsd.lib.mk>.  It contains overrides that are used when building
504the NetBSD source tree.  For instance, if "PARALLEL" is defined by
505the program/library Makefile, it includes a set of rules for lex and
506yacc that allow multiple lex and yacc targets to be built in parallel.
507
508Other variables of note (incomplete list):
509
510WARNS		Crank up gcc warning options; WARNS=1 and WARNS=2 are the two
511		distinct levels.
512
513FORMAT_AUDIT	If FORMAT_AUDIT is set, and WFORMAT is set and > 1, turn on
514WFORMAT 	-Wnetbsd-format-audit for extra-stringent format checking.
515		WFORMAT belongs in individual makefiles and/or Makefile.inc files.
516		(set WFORMAT=1 in individual makefiles if a program is
517		not security critical and is doing bizarre things with
518		format strings which would be even uglier if rewritten)
519		FORMAT_AUDIT should go in mk.conf if you're doing format-string auditing.
520		FORMAT_AUDIT may go away in time.
521
522=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
523
524The include file <bsd.lib.mk> has support for building libraries.  It has
525the same eight targets as <bsd.prog.mk>: all, clean, cleandir, depend,
526includes, install, lint, and tags.  Additionally, it has a checkver target
527which checks for installed shared object libraries whose version is greater
528that the version of the source. It has a limited number of suffixes,
529consistent with the current needs of the BSD tree.
530
531It sets/uses the following variables:
532
533LIB		The name of the library to build.
534
535LIBDIR		Target directory for libraries.
536
537LINTLIBDIR	Target directory for lint libraries.
538
539LIBGRP		Library group.
540
541LIBOWN		Library owner.
542
543LIBMODE		Library mode.
544
545LDADD		Additional loader objects.
546
547MAN		The manual pages to be installed (use a .1 - .9 suffix).
548
549MKLINKLIB	If "no", act as "MKPICINSTALL=no MKPROFILE=no".
550		Also:
551			- don't install the .a libraries
552			- don't install _pic.a libraries on PIC systems
553			- don't build .a libraries on PIC systems
554			- don't install the .so symlink on ELF systems
555		I.e, only install the shared library (and the .so.major
556		symlink on ELF).
557
558MKPICLIB	If "no", don't build _pic.a libraries, and build the
559		shared object libraries from the .a libraries.  A
560		symlink is installed in ${DESTDIR}/usr/lib for the
561		_pic.a library pointing to the .a library.
562
563NOCHECKVER_<library>
564NOCHECKVER	If set, disables checking for installed shared object
565		libraries with versions greater than the source.  A
566		particular library name, without the "lib" prefix, may
567		be appended to the variable name to disable the check for
568		only that library.
569
570SRCS		List of source files to build the library.  Suffix types
571		.s, .c, and .f are supported.  Note, .s files are preferred
572		to .c files of the same name.  (This is not the default for
573		versions of make.)
574
575The include file <bsd.lib.mk> includes the file named "../Makefile.inc"
576if it exists, as well as the include file <bsd.man.mk>.
577
578It has rules for building profiled objects; profiled libraries are
579built by default.
580
581Libraries are ranlib'd when made.
582
583=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
584
585The include file <bsd.obj.mk> defines targets related to the creation
586and use of separated object and source directories.
587
588If an environment variable named MAKEOBJDIRPREFIX is set, make(1) uses
589${MAKEOBJDIRPREFIX}${.CURDIR} as the name of the object directory if
590it exists.  Otherwise make(1) looks for the existance of a
591subdirectory (or a symlink to a directory) of the source directory
592into which built targets should be placed.  If an environment variable
593named MAKEOBJDIR is set, make(1) uses its value as the name of the
594object directory; failing that, make first looks for a subdirectory
595named "obj.${MACHINE}", and if that doesn't exist, it looks for "obj".
596
597Object directories are not created automatically by make(1) if they
598don't exist; you need to run a separate "make obj".  (This will happen
599during a top-level build if "MKOBJDIRS" is set to a value other than
600"no").  When the source directory is a subdirectory of ${BSDSRCDIR} --
601and this is determined by a simple string prefix comparison -- object
602directories are created in a separate object directory tree, and a
603symlink to the object directory in that tree is created in the source
604directory; otherwise, "make obj" assumes that you're not in the main
605source tree and that it's not safe to use a separate object tree.
606
607Several variables used by <bsd.obj.mk> control exactly what
608directories and links get created during a "make obj":
609
610MAKEOBJDIR	If set, this is the component name of the object
611		directory.
612
613OBJMACHINE	If this is set but MAKEOBJDIR is not set, creates
614		object directories or links named "obj.${MACHINE}";
615		otherwise, just creates ones named "obj".
616
617USR_OBJMACHINE  If set, and the current directory is a subdirectory of
618		${BSDSRCDIR}, create object directory in the
619		corresponding subdirectory of ${BSDOBJDIR}.${MACHINE};
620		otherwise, create it in the corresponding subdirectory
621		of ${BSDOBJDIR}
622
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624
625The include file <bsd.kernobj.mk> defines variables related to the
626location of kernel sources and object directories.
627
628KERNSRCDIR	Is the location of the top of the kernel src.
629		It defaults to ${BSDSRCDIR}/sys, but the top-level
630		Makefile.inc sets it to ${ABSTOP}/sys (ABSTOP is the
631		absolute path to the directory where the top-level
632		Makefile.inc was found.
633
634KERNARCHDIR	Is the location of the machine dependent kernel
635		sources.  It defaults to arch/${MACHINE}
636		
637KERNCONFDIR	Is where the configuration files for kernels are
638		found; default is ${KERNSRCDIR}/${KERNARCHDIR}/conf.
639
640KERNOBJDIR	Is the kernel build directory.  The kernel GENERIC for
641		instance will be compiled in ${KERNOBJDIR}/GENERIC.
642		The default value is
643		${MAKEOBJDIRPREFIX}${KERNSRCDIR}/${KERNARCHDIR}/compile
644		if it exists or the target 'obj' is being made.
645		Otherwise the default is
646		${KERNSRCDIR}/${KERNARCHDIR}/compile.
647
648It is important that Makefiles (such as those under src/distrib) that
649wish to find compiled kernels use bsd.kernobj.mk and ${KERNOBJDIR}
650rather than make assumptions about the location of the compiled kernel.
651
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653